A through-hole is provided in a vehicle body panel (dash panel) for partitioning an engine room side and a passenger room side in a motor vehicle. In the case where a wire harness is passed through the through-hole and is wired in the vehicle body, a grommet made of rubber or elastomer is mounted on the wire harness and is disposed between the wire harness and the through-hole to protect the wire harness and to carry out waterproofing, soundproofing, and dustproofing from the engine room side to the passenger room side.
An example of a grommet 2 shown in FIG. 6 has been used generally. The grommet 2 includes a smaller diameter tubular section 2a, a larger diameter tubular section 2b connected to an end of the smaller diameter tubular section 2a, and a wire harness passing section 2c in a hollow space along an axial direction of the sections 2a and 2b. The larger diameter tubular section 2b is provided on an outer periphery with a vehicle body latching recess 2d. The recess 2d is provided on side end with a lip 2e. The grommet 2 seals a through-hole 1a in a vehicle body 1 by press-contacting the lip 2e to the vehicle body 1.
When the grommet 2 is inserted from the engine room side A through the through-hole 1a to the passenger room side B, the lip 2e is deflected to catch a bottom surface of the vehicle body latching recess 2d and an inner peripheral surface around the through-hole 1a. This will cause the grommet 2 to be mounted on the vehicle body 1 incorrectly. Consequently, after the whole of the larger diameter tubular section 2b is inserted into the through-hole 1a and is pushed into the passenger room side B temporarily, the section 2b is pulled back again to engage the vehicle body latching recess 2d with the through-hole 1a, thereby preventing the lip 2e from catching the surfaces.
However, since a strong force is required to force the larger diameter tubular section 2d to be inserted into the passenger room side B, workability will be lowered significantly and efficiency in an attaching work will be lowered. Since the grommet 2 shown in FIG. 6 is not provided with a sound insulation means for preventing and restraining noises from being transmitted from the engine room side to the passenger room side, the grommet cannot reply to a demand for quiet in the passenger room side.
In order to overcome the above problems, JP HEI 3 (1991)-9214 U (Patent Document 1) has proposed a grommet 3 shown in FIGS. 7A and 7B. The grommet 3 is provided with a dual seal structure that exerts sound insulation.
The grommet 3 is attached to a through-hole 1a in a vehicle body panel 1 on which a sound insulation material 1b is laminated at a passenger room side B. The grommet 3 includes a first tubular seal section 3d that seals the through-hole 1a at an engine room side A and a second flange-like seal section 3e that seals an opening of the sound insulation material 1b opposed to the through-hole 1a, a larger diameter tubular section 3a, and smaller diameter tubular sections 3b and 3c that protrude from an outer periphery of the larger diameter tubular section 3a to clamp a wire harness W/H onto opposite ends of the larger diameter tubular section 3a. The second seal section 3e is provided at on a surface at the passenger room side B with a projection 3f that can be held by a tool.
As shown in FIG. 7B, when the grommet 3 is attached to the through-hole 1a, the grommet 3 together with the wire harness W/H is inserted into the through-hole 1a from the engine room side A, the first seal section 3d is brought into contact with the vehicle body panel 1 and the projection 3f of the second seal section 3e is protruded from the through-hole 1a to the passenger room side B. Then, the projection 3f is pulled from the passenger room side B, the whole of the second seal section 3e is drawn out from the through-hole 1a, and a peripheral edge of the second seal section 3e is brought into contact with the sound insulation material 1b. 
Although the grommet 3 requires no undue pushing work described above upon attachment, it is necessary to simultaneously carry out a work for pushing the wire harness W/H from the engine room side A and a work for pulling the projection 3f from the passenger room side B to draw out the second seal section 3e from the through-hole 1a. This requires a working person at each of the engine room side A and the passenger room side B. This will lower workability.    Patent Document 1: JP HEI 3 (1991)-9214 U